FTY720 Abrogates Collagen-Induced Arthritis by Hindering Dendritic Cell Migration to Local Lymph Nodes

Because dendritic cells (DCs) play critical roles in the pathogenesis of rheumatoid arthritis, modulation of their functions could serve as a novel therapy. In this study, we demonstrated that FTY720 treatment significantly suppressed the incidence and severity of collagen-induced arthritis (CIA) in DBA/1J mice via the modulation of DC functions. In FTY720-treated CIA mice, a decrease in the number of DCs in local draining lymph nodes (LNs) was observed. In vitro, FTY720 inhibited the trafficking of LPS-stimulated bone marrow-derived DCs (BMDCs). Decreased secretion of CCL19 and downregulation of CCR7 on DCs may explain the mechanisms underlying the impairment of DC migration induced by FTY720. In a DC-induced mouse arthritis model, FTY720 treatment also suppressed the incidence and severity of arthritis, which was correlated with a decrease in the migration of injected BMDCs to draining LNs. Although lower levels of costimulatory molecules (CD40, CD80, and CD86) and I-A(q) expressed on LN DCs were observed in FTY720-treated mice, in vitro analysis showed no effect of FTY720 on LPS-stimulated BMDC maturation. Furthermore, LN cells from FTY720-treated CIA mice displayed diminished production of proinflammatory cytokines in response to collagen II and Con A stimulation. In addition, the ratio of Th1/Th2 in the draining LNs of mice with DC-induced arthritis was decreased upon FTY720 treatment. This finding was consistent with the fact that FTY720 suppressed IL-12p70 production in cultured BMDCs. Taken together, these results indicate that inhibition of DC migration by FTY720 may provide a novel approach in treating autoimmune diseases such as rheumatoid arthritis.